Simultaneous enrichment and speciation of lead and mercury by magnetic solid-phase extraction coupled to HPLC-ICP-MS based on magnetic hydrazine-linked covalent organic frameworks.

BACKGROUND: Trace levels of organic and inorganic lead and mercury species in the environment, including divalent lead (Pb2+), trimethyllead (TML), divalent mercury (Hg2+), monomethylmercury (MeHg), and ethylmercury (EtHg), are highly toxic to humans and ecology. It is of great importance for speciation of lead and mercury to evaluate the toxicity of lead and mercury and their biogeochemistry in the environment. However, simultaneous multi-elemental enrichment and speciation at trace level remains a challenge. There are few reports of simultaneous magnetic solid-phase extraction (MSPE) of organic and inorganic lead and mercury species at trace level in the real water. RESULTS: In this work, a novel core-shell magnetic hydrazine-linked covalent organic frameworks (Fe3O4@COF-TCH) was prepared for the first time by grafting hydrazine-linked COFs on the Fe3O4 nanoparticles. Fe3O4@COF-TCH with abundant thione and imino groups has strong adsorption for lead and mercury species. Based on it, a simple and practical magnetic solid-phase extraction high-performance liquid chromatography-inductively coupled plasma mass spectrometry (MSPE-HPLC-ICP-MS) method was developed for extraction and determination of trace lead and mercury species, including Hg2+, MeHg, EtHg, Pb2+ and TML. The limits of detection (3δ) of the developed method were 0.08, 0.81, 0.90, 0.56 and 0.88 ng L-1 with the enrichment factors (EFs) of 384, 376, 379, 389 and 360-fold for Pb2+, TML, Hg2+, MeHg and EtHg, respectively. The high accuracy and reproducibility have been proved by the spiked recoveries (94.4-103 %) in real samples. SIGNIFICANCE: The proposed method with simple operation and high sensitivity has been successfully applied to simultaneous speciation of lead and mercury at trace levels in the water samples with complicated matrices, including underground water, surface water, sea water. Meanwhile, it has the advantages of cost-saving, labor-saving and time-saving and is suitable for the investigation and risk assessment in water. The development of MSPE-HPLC-ICP-MS method provides ideas and guidance for the simultaneous multi-elemental enrichment and speciation.

Rapid, easy and catalyst-free preparation of magnetic thiourea-based covalent organic frameworks at room temperature for enrichment and speciation of mercury with HPLC-ICP-MS.

The complex and cumbersome preparation of magnetic covalent organic frameworks (COFs) nanocomposites on a small scale limits their application. Herein, a rapid and easy route was employed for the preparation of magnetic thiourea-based COFs nanocomposites. COFs were coated on Fe3O4 nanoparticles at room temperature without a catalyst within approximately 30 min. This method is suitable for the large-scale preparation of magnetic adsorbent. Using the as-prepared magnetic adsorbent (Fe3O4@COF-TpTU), we developed a simple, efficient, and sensitive magnetic solid-phase extraction-high performance liquid chromatography-inductively coupled plasma-mass spectrometry (MSPE-HPLC-ICP-MS) for the enrichment and determination of mercury species, including Hg2+, methylmercury (MeHg), and ethylmercury (EtHg). The effects of the experimental parameters on the extraction efficiency, including solution pH, adsorption and desorption time, composition and volume of the elution solvent, salinity, coexisting ions, and dissolved organic matter, were comprehensively investigated. Under optimised conditions, the limits of detection in the developed method were 0.56, 0.34, and 0.47 ng L-1 with enrichment factors of 190, 195, and 180-fold for Hg2+, MeHg, and EtHg, respectively. The satisfactory spiked recoveries (97.0-103%) in real water samples and high consistency between the certified and determined values in a certified reference material demonstrate the high accuracy and reproducibility of the developed method. The as-proposed method with simple operation, high sensitivity, and excellent anti-matrix interference performance was successfully applied to the enrichment and determination of trace levels of mercury species in the natural samples with complicated matrices, such as underground water, surface water, seawater and biological samples.

Highly sensitive quantification of ultratrace As(V) via iEESI-MS.

Arsenate (As(V)) is a fatal poison and is widely distributed in the environment. The quick and accurate determination of As(V) is of great importance. Herein, we developed a novel competitive coordination strategy for the quantification of ultratrace As(V) using online internal extractive electrospray ionization mass spectrometry (iEESI-MS). Our strategy demonstrates great success for direct ultratrace As(V) detection in broad types of samples, from solids to liquids, such as food, water and biological samples.